Thermal printing head comprising a printable tape guiding member, in the form of a protection cover for a flexible control printed circuit

ABSTRACT

A thermal printing head comprises a guide member made in a single-piece and designed as a jumper comprising two superimposed walls, covering, at least partly, respectively and jointly both surfaces of a flexible printed circuit board and providing between them a space for the passage of the support guide wing, enclosed by the flexible printed circuit board, such that the guide member can be elastically nested on the guide wing of the support and provides protection for the flexible printed circuit board in the zone of its junction with the support, and such that, one of the walls of the guide member comprising fingers producing localized elastic pressure on the flexible printed circuit board, an electric contact is provided between the flexible printed circuit board and the support for grounding the printing head via the flexible printed circuit.

The invention relates to the field of thermal printing machines, notablyapplicable to payment terminals. Its object is a member for guiding atape to be printed, equipping a printing head for such machines.

Thermal printing mechanisms are known, which include a supportaccommodating means for driving a tape to be printed against a thermalprinting head, and means for controlling the dynamic members of themechanism from remote control means. Among those mechanisms, thosewherein the printing head includes a rigid support, carrying a printingmember made of ceramic material and a printable tape guiding member, areknown more particularly. The control means are formed, according todiverse variations, either of a rigid plate fixed to the support, saidrigid plate incorporating a printed circuit, or of a flexible printedcircuit within which is embedded such a circuit, the flexible printedcircuit being fixed to the printing member by means of spikes or weldedthereto, notably.

The difficulties to overcome in the field lie in a structuralorganisation of the printing head which should be simple and with smallspace requirements. Consequently, a preferred solution consists in usinga flexible connector for the control means. However, the fragility ofthe flexible printed circuit, and its tricky linkage with the printinghead, and notably with the printing member, tend to affect theadvantages offered by their use, by reason of particular arrangements ofthe printing head aiming to protect the flexible printed circuit and tosecure, possibly even reinforce, its link with the printing head.

Besides, a general problem to solve lies in grounding the variousmembers participating in the printing mechanism. More particularly asregards the printing head, the former is especially fragile and might bedamaged following electrostatic discharges from the surroundingelements, which said head supports and/or includes, including the tapeto be printed.

It has been suggested by the document EP 0729839 (ROHM CO Ltd) to add-onby fitting on the support, a metallic guiding member for the tape to beprinted, said guiding member comprising spikes extending across a rigidprinted circuit forming the printing head control means, via openingsthat it includes. These spikes make it possible to provide an electriccontact between the conducting support and the guiding member, which isalso conducting, and hence between the support and the tape to beprinted, with a view to evacuating the static electricity transported bysaid tape.

The general purpose of the present invention is to provide simplearrangements of the printing head to remedy all the aforementionedshortcomings. More precisely, it is an object of the present inventionto organise the structure of the printing head so as to make thestructure thereof as straightforward as possible and with the smallestspace requirements possible, where such organisation makes it possible,moreover, to protect easily its sensitive members, notably the printingmember and the control means, from a mechanical viewpoint as well asfrom the point of view of the electrostatic charges transported by thevarious members involved therein.

More particularly, a first specific aim of the present invention is toprovide a thermal printing head arranged in order to secure the mechaniclink of the various elements involved therein and in order to protectthe sensitive members thereof, notably the control means and printingmember, such that this arrangement is not detrimental to asimplification of its organisation nor to its small space requirements.

More particularly still, a second aim of the present invention is toprovide a thermal printing head whose simple organisation and smallspace requirements make it possible to implement specific configurationsto protect its sensitive members against the electrostatic chargespresent in its environment when in use.

The thermal printing head of the present invention is intended forequipping a printing mechanism of a tape to be printed, such as may beapplied to payment terminals.

This printing head includes a rigid support carrying a printing membermade of ceramic material, a member for guiding a tape to be printed andmeans for controlling the printing head. The guiding member is added tothe rigid support by fitting.

According to a first approach of the present invention, the controlmeans are composed of a flexible printed circuit fixed to the printingmember. The support comprises a wing for guiding the flexible printedcircuit, around which it extends partially from one large face to theother large face thereof. The guiding member, for its part, isadvantageously arranged into a protection cover for the guiding wing ofthe support, enveloped by the flexible printed circuit. The guidingmember is advantageously added to the guiding wing by fitting, notablyelastic fitting, in order to cap at least partially and jointly theflexible printed circuit and the opposed large faces of the guidingwing. These configurations are such that the flexible printed circuit isoriented with a 180° return from its fastening zone to the printingmember towards the outside of the printing head, while remainingprotected by the guiding member.

According to an advantageous embodiment, the guiding member is formedadvantageously in the general shape of a jumper, whereas its assembly byfitting on the support is performed at least by pinching the guidingwing using the guiding member between the opposite tabs of the jumper,which are preferably elastically mobile or which include, similarly,elastically antagonist members.

According to a second approach of the present invention, the controlmeans are formed of a flexible printed circuit fixed to the printingmember which is used for grounding the support by using a contactestablished between a bare zone of the flexible printed circuit and thesupport, and/or similarly between a bare zone of the flexible printedcircuit and the control member, itself in electric contact with thesupport. This electric contact is caused by a corresponding localisedpressure exerted on the flexible printed circuit by at least one fingerwith which the guiding member is provided.

It should be noted that the aforementioned organization of themechanical link between the guiding member on the one hand, and theflexible printed circuit and the support on the other hand, makes itpossible, advantageously, to provide a simple contact between thesupport and the flexible printed circuit, by using the guiding member.

According to this second approach of the present invention, the printinghead is of the type wherein the guiding member is added to the supportin order to provide an electric contact therebetween, for at leastevacuating the electrostatic charges transported by the tape to beprinted. It will be understood that the guiding member and the supportare electrically conducting.

According to an aspect of the invention relating to this secondapproach, the control means are formed of a flexible printed circuitfixed to the printing member, and the guiding member of the printabletape is exploited for grounding the printing head via a flexible printedcircuit. This guiding member comprises advantageously at least onefinger, and notably a plurality thereof, for bearing locally on theflexible printed circuit. This local bearing effect establishes anelectric contact between the flexible printed circuit and at least oneof the support and the guiding member, for grounding the printing headvia the flexible printed circuit.

It will be understood that the conducting property of any of the supportand the guiding member may be limited structurally to only their zonesdesired to be conducting.

It will be understood that according to an advantageous embodimentcombining both approaches aforementioned, the inner face of the guidingmember includes said localised bearing member, arranged on thecorresponding tab of the jumper.

According to a preferred embodiment of the support, said supportincludes a generally L-shaped profile. A first wing of the supportcarries, superimposed, the printing member made of ceramic material,which is notably designed as a plate. A second wing of the support,concurrent to the former, and notably substantially orthogonal, formsthe guiding wing of the flexible printed circuit.

The flexible printed circuit is preferably fixed to the printing memberby welding, the guiding member comprising advantageously at least onewall for covering the flexible printed circuit at least partially in itszone for covering the support. The covering wall that overlaps theflexible printed circuit in the vicinity of its welding zone is providedwith at least one member for protecting the welding zones on theprinting member of the flexible printed circuit, and/or, whereappropriate, of their immediate vicinity.

The assembly by fitting of the guiding member on the support ispreferably a fitting that is difficult to reverse, and preferablyspontaneously irreversible, such as by using a clip or similar.

For example, the assembly by fitting of the guiding member on thesupport is comforted by a member for fitting the guiding member inside acorresponding recess of the support. It will be noted that themechanical and electric link between the guiding member and the supportis accessorily completed by means of lateral walls of the guidingmember, in contact with the corresponding edges of the support.

The guiding member comprises preferably a recess facing a window of thesupport, for letting through an optical signal from a member detectingthe tape to be printed. It will be noted that, where appropriate, thisrecess of the guiding member also enables the passage of a protrudingoptic detection member, which is advantageously supported by theflexible printed circuit.

It will be observed that according to another aspect of the inventionrevealing another of its advantages, the aforementioned configurations,taken individually or in combination, may be obtained by a simplearrangement of the printable tape guiding member and/or of the support,which are formed independently by a monobloc element.

According to a first embodiment of this arrangement, any of the supportand/or of the guiding member is formed by cutting and folding a metalsheet.

According to a second embodiment variation of this arrangement, any ofthe support and/or of the guiding member is formed by moulding aconducting plastic material, the latter being either charged or providedwith a conducting coating in order to be globally conducting, orincorporating conducting members embedded during the moulding operation.

The present invention will be better understood and relevant detailswill appear in light of the following description of a preferredembodiment, in relation with the appended drawings, wherein:

FIG. 1 is an exploded top view in perspective of a printing headaccording to a first embodiment of the invention.

FIG. 2 is a top view in perspective of the printing head represented onFIG. 1, partially assembled.

FIG. 3 is a bottom view in perspective of the printing head representedon FIG. 1 and FIG. 2, partially assembled.

FIG. 4 is an exploded top view in perspective of a printing headaccording to a second preferred embodiment of the invention.

FIG. 5 is a top view in perspective of the printing head represented onFIG. 1, partially assembled.

FIG. 6 is a bottom view in perspective of the printing head representedon FIG. 1 and FIG. 2, partially assembled.

On the Figures, a thermal printing head is mainly composed of aconducting support 1, a printing member of ceramic material 2, aflexible printed circuit 3 and a conducting guiding member 4 for arunning printable tape (not represented on the Figures).

The support 1 includes two orthogonal wings 5 and 6, whereof a firstwing 5 which is provided for supporting a plate 2 made of ceramicmaterial, forming the printing member, and a second wing 6 which isprovided to be enveloped by the flexible printed circuit 3, from one ofits large faces to the other. The flexible printed circuit 3 comprisesfastening tabs 7, 7′, 7″ for fixing to the printing member 2 by welding.It is visible that the 180° return of the flexible printed circuit 3from its fastening zone makes it possible to avoid subjecting thewelding zones to a detrimental tension liable to alter the fasteningquality of the flexible printed circuit to the printing member.

The guiding member 4 is arranged as a cover for protecting the flexibleprinted circuit 3, and includes, to this end, two superimposed walls 8and 9 to cover both faces of the flexible printed circuit 3 in contactwith the second wing 6 of the support 1.

The wall 8 for covering the flexible printed circuit 3 in its fasteningzone to the printing member 2 comprises members 10 a, 10 b, 10 c, 10 d,10 e (first variation, FIG. 1 to FIG. 3) or 20 a, 20 b (secondvariation, FIG. 4 to FIG. 6) for protecting the welding zones.

Certain zones of these protection members, possibly certain of thesemembers properly speaking according to the first variation illustrated,are for example allocated to the protection of the welding zones of theflexible printed circuit 3 for increased tear strength; other zones ofthese protection members, possibly certain of these members properlyspeaking according to the first illustrated variation, are for exampleallocated to covering the vacant space between electronic members, suchas 16, 16′, supported by and protruding from the printing member 2, andthe neighbouring edge of the corresponding wall 8 of the guiding member4 covering the flexible printed circuit 3, in order to prevent thedetrimental ingress of dirt or dust.

Besides, the guiding member 4 includes fingers 11, 11′, 11″ (firstvariation, FIG. 1 to FIG. 3) or 21, 21′, 21″, 21′″ (second variation,FIG. 4 to FIG. 6), for localised bearing on the flexible printed circuit3. It will be understood that this localisation of the bearing fingers11, 11′, 11″ or 21, 21′, 21″, 21′″ matches corresponding zones of theflexible printed circuit for grounding purposes. These bearing fingersmake it possible to establish reliable electric contact between thesupport 1 and the flexible printed circuit 3.

The guiding member 4 is in electric contact with the support 1, via atleast one member 17 (first and second variations, FIG. 1 to FIG. 6)and/or 22 (second variation, FIG. 4 to FIG. 6) with which it isprovided, for fitting inside a corresponding housing 18 and/or 23 of thesupport 1. This electric contact is preferably enhanced by contactingthe lateral walls 12, 12′ of the guiding member 4, with thecorresponding edges 13, 13′ of the support 1. Consequently, the printinghead is globally grounded, including the running tape in contact withthe guiding member 4.

The conducting support 1 being liable to be in electric contact with thechassis of the printing mechanism (not represented on the Figures) whichsupports the head, the printing mechanism may therefore be grounded bythe guiding member 4 of the printable tape bearing against the flexibleprinted circuit 3, for electric contact thereof 3 with the support 1.

It will be observed on the guiding member 4, covering the flexibleprinted circuit 3, the presence of a recess 14 facing a correspondingwindow 15 of the support 1. This recess 14 is provided for the passageof an optic member 19 supported by the flexible printed circuit 3, or atleast of its signal, for detecting the presence of the printable tape.

According to the first embodiment variation illustrated on FIG. 1 toFIG. 3, the support 1 and the guiding member 4 are formed by cutting andfolding a metal sheet.

The bearing fingers 11, 11′, 11″, the protection members 10 a, 10 b, 10c and 10 d, and the fitting member 17 notably, extend from the walls 8and 9 of the guiding member provided for covering the flexible printedcircuit 3.

According to the second embodiment variation illustrated on the FIG. 4to FIG. 6, the support 1 and the guiding member 4 are formed by mouldinga plastic material, made conducting by coating or charging, the bearingfingers 21, 21′, 21″, 21′″, the protection members 20 a, 20 b and theembedding members 17 and 23 notably, being formed when moulding theguiding member 4.

There will be recognised therefore in its entirety a printable tapeguiding member 4 for a thermal printing head in that it is monobloc andformed into a jumper having two superimposed walls 8 and 9 for covering,at least partially, respectively and jointly, both faces of the flexibleprinted circuit 3, said superimposed walls 8 and 9 providingtherebetween a space for the passage of the guiding wing 6 of thesupport, enveloped by the flexible printed circuit 3, so that the jumperdesign of the guiding member 4 makes it possible to elastically fit iton the guiding wing 6 of the support 1 and makes it possible to protectthe flexible printed circuit 3 in its junction zone with the support 1,including and advantageously in its welding zones to the printing member2, and so that, one of the walls 8 of the guiding member 4 includingfingers 11 or 21 for bearing locally on the flexible printed circuit 3,an electric contact is established between the flexible printed circuit3 and the support 1, for grounding the printing head via the flexibleprinted circuit 3.

The guiding member 4 comprises moreover at least one fitting member 17,12, 22 for mechanic and electric linkage with the support 1, viaco-operating members 18, 13, 23 with which it is provided. The wall 8 ofthe guiding member 4 intended for covering the flexible printed circuit3 in the vicinity of its fastening by welding to the printing member 2,is provided with members 10 for protecting the welding zones.

The wall 9, opposed to the previous one 8, of the guiding member 4comprises elastic bearing fingers 11, 11′, 11″ or 21, 21′, 21″ forobtaining an electric contact between the support 1 and the flexibleprinted circuit 3, for grounding the printing head.

1. A thermal printing head for printing mechanism of a printable tape,said head comprising: (i) a rigid support, said support including a bodyand a guiding wing, (ii) a printing member carried by the support, (iii)a flexible printed circuit fixed to the printing member for controllingthe printing head, at least a portion of said flexible printed circuitextending around the guiding wing of the support and over both largeopposite faces of the guiding wing in at least a portion of the guidingwing, and (iv) a guiding member for a printable tape, wherein theguiding member is designed as a protection cover for this guiding wingenveloped by the flexible printed circuit, and the guiding member isfitted over the portion of the flexible printed circuit jointly with theportion of the guiding wing, so as to cap that portion of the flexibleprinted circuit jointly with the large opposite faces of the guidingwing of the support in that portion of the guiding wing, so that theflexible printed circuit is oriented with a 180° return from a fasteningzone to the printing member towards the outside of the printing head,while remaining at least partially protected by the guiding member.
 2. Aprinting head according to claim 1, wherein the guiding member is in thegeneral shape of a jumper, its assembly by fitting on the support beingperformed at least by pinching the guiding wing using the guiding memberbetween the opposite tabs of the jumper.
 3. A printing head according toclaim 1, wherein the guiding member is added to the rigid support byfitting so as to establish an electric contact therebetween for at leastevacuating the electrostatic charges transported by the printable tape,the guiding member and the supporting board being conducting and thecontrol means being composed of a flexible printed circuit fixed to theprinting member, the printable tape guiding member comprises at leastone finger for bearing locally on the flexible printed circuit, so as toestablish an electric contact between the flexible printed circuit andat least one of the support and the guiding member, for grounding theprinting head via the flexible printed circuit.
 4. A thermal printinghead according to claim 1, wherein the support has a generally L-shapedprofile, whereof a first wing carries, superimposed, the printing membermade of ceramic material, which is arranged as a plate, and whereof asecond wing, concurrent to the former, makes up the guiding wing of theflexible printed circuit.
 5. A thermal printing head according to claim1, wherein the flexible printed circuit being fixed to the printingmember by welding, the guiding member comprises at least one wall forcovering the flexible printed circuit at least partially in its zonecovering the supporting board, the covering wall that covers theflexible printed circuit in the vicinity of its welding zone beingprovided with at least one member protecting the welding zones of theflexible printed circuit on the printing member.
 6. A thermal printinghead according to claim 1, wherein the assembly of the guiding member byfitting on the support is comforted by a member for fitting the guidingmember, said fitting member being fitted inside a corresponding recessof the support.
 7. A thermal printing head according to claim 1, whereinthe guiding member comprises a recess facing a window of the recess, forletting through an optical signal from a member for detecting the tapeto be printed.
 8. A thermal printing head according to claim 1, whereinat least one of the printable tape guiding member and the support isformed by cutting and folding a metal sheet.
 9. A thermal printing headaccording to claim 1, wherein at least one of the printable tape guidingmember and the support is formed by moulding a conducting plasticmaterial.
 10. A printable tape guiding member for thermal printing headaccording to claim 1, which is monobloc and formed into a jumpercomprising two superimposed walls providing therebetween a space for thepassage of the guiding wing of the support, enveloped by the flexibleprinted circuit, so that the jumper design of the guiding member makesit possible to elastically fit the guiding member on the guiding wing ofthe support and so that, one of the walls of the guiding memberincluding fingers for bearing locally on the flexible printed circuit,an electric contact can be established between the flexible printedcircuit and the support, for grounding the printing head via theflexible printed circuit.
 11. A printing head according to claim 1,wherein the printing member is made of ceramic material.
 12. A printinghead according to claim 1, wherein the support comprises (i) asupporting wing carrying the printing member and (ii) the guiding wing.13. A printing head according to claim 12, wherein the support isgenerally L-shaped with the supporting wing forming one branch of the Land the guiding wing forming the other branch of the L.
 14. A printinghead according to claim 13, wherein the wings are substantiallyorthogonal to each other.
 15. A printing head according to claim 1,wherein the flexible printed circuit extends over substantially thetotality of both large faces of the guiding wing.
 16. A printing headaccording to claim 15, wherein the guiding member is fitted over theflexible printed circuit jointly with substantially the totality of bothlarge faces of the guiding wings so as to cap the flexible printedcircuit jointly with substantially the totality of the large oppositefaces of the guiding wing.